Andrei P. Igoshev

University of Leeds · Department of Applied Mathematics

Magnetars are neutron stars (NSs) with extreme magnetic fields¹ of strength 5 × 10¹³−10¹⁵ G. These fields are generated by dynamo action during the proto-NS phase, and are expected to have both poloidal and toroidal components2–6, although the energy of the toroidal component could be ten times larger⁷. Only the poloidal dipolar field can be measur...

Neutron stars are natural physical laboratories allowing us to study a plethora of phenomena in extreme conditions. In particular, these compact objects can have very strong magnetic fields with non-trivial origin and evolution. In many respects, its magnetic field determines the appearance of a neutron star. Thus, understanding the field propertie...

Supernova explosion and the associated neutron star natal kicks are important events on a pathway of a binary to become a gravitational wave source, an X-ray binary or a millisecond radio pulsar. Weak natal kicks often lead to binary survival, while strong kicks frequently disrupt the binary. In this article, we aim to further constrain neutron sta...

Initial distributions of pulsar periods and magnetic fields are essential components of multiple modern astrophysical models. Not enough work has been done to properly constrain these distributions using direct measurements. Here we aim to fill this gap by rigorously analysing properties of young neutron stars associated to supernova remnants. In o...

We numerically model evolution of magnetic fields inside a neutron star under the influence of ambipolar diffusion in the weak-coupling mode in the one-fluid MHD approximation. Our simulations are three-dimensional and performed in spherical coordinates. Our model covers the neutron star core and includes crust where the magnetic field decay is due...

Off-centred dipole configurations have been suggested to explain different phenomena in neutron stars, such as natal kicks, irregularities in polarisation of radio pulsars and properties of X-ray emission from millisecond pulsars. Here for the first time we model magneto-thermal evolution of neutron stars with crust-confined magnetic fields and off...

Off-centred dipole configurations have been suggested to explain different phenomena in neutron stars, such as natal kicks, irregularities in polarisation of radio pulsars and properties of X-ray emission from millisecond pulsars. Here for the first time we model magneto-thermal evolution of neutron stars with crust-confined magnetic fields and off...

The speeds of young isolated pulsars are generally inferred from their observed 2D velocities on the plane of the sky under the assumption that the unobserved radial velocity is not special, i.e., that the measured 2D velocity is an isotropic projection of the full 3D velocity. However, if pulsar spins are preferentially aligned with kicks, then th...

Type Ia and other peculiar supernovae (SNe) are thought to originate from the thermonuclear explosions of white dwarfs (WDs). Some of the proposed channels involve the ejection of a partly exploded WD (e.g. Iax SN remnant) or the companion of an exploding WD at extremely high velocities (>400 km s−1). Characterisation of such hyper-runaway/hypervel...

We numerically model evolution of magnetic fields inside a neutron star under the influence of ambipolar diffusion in the weak-coupling mode in the one-fluid MHD approximation. Our simulations are three-dimensional and performed in spherical coordinates. Our model covers the neutron star core and includes crust where the magnetic field decay is due...

The speeds of isolated pulsars are generally inferred from their observed 2-d velocities on the plane of the sky under the assumption that the unobserved radial velocity is not special, i.e., that the measured 2-d velocity is an isotropic projection of the full 3-d velocity. However, if pulsar spins are preferentially aligned with kicks, then the o...

Type Ia and other peculiar supernovae (SNe) are thought to originate from the thermonuclear explosions of white dwarfs (WDs). Some of the proposed channels involve the ejection of a partly exploded WD (e.g. Iax SN remnant) or the companion of an exploding WD at extremely high velocities (>400 km s$^{-1}$). Characterisation of such hyper-runaway/hyp...

Initial distributions of pulsar periods and magnetic fields are essential components of multiple modern astrophysical models. Not enough work has been done to properly constrain these distributions using direct measurements. Here we aim to fill this gap by rigorously analysing properties of young neutron stars associated to supernova remnants. In o...

Neutron stars host the strongest magnetic fields that we know of in the Universe. Their magnetic fields are the main means of generating their radiation, either magnetospheric or through the crust. Moreover, the evolution of the magnetic field has been intimately related to explosive events of magnetars, which host strong magnetic fields, and their...

Neutron stars host the strongest magnetic fields that we know of in the Universe. Their magnetic fields are the main means of generating their radiation, either magnetospheric or through the crust. Moreover, the evolution of the magnetic field has been intimately related to explosive events of magnetars, which host strong magnetic fields, and their...

Supernova explosion and the associated neutron star natal kicks are important events on a pathway of a binary to become a gravitational wave source, an X-ray binary or a millisecond radio pulsar. Weak natal kicks often lead to binary survival, while strong kicks frequently disrupt the binary. In this article, we aim to further constrain neutron sta...

Neutron stars are natural physical laboratories allowing us to study a plethora of phenomena in extreme conditions. In particular, these compact objects can have very strong magnetic fields with non-trivial origin and evolution. In many respects its magnetic field determines the appearance of a neutron star. Thus, understanding the field properties...

Stars of spectral types O and B produce neutron stars (NSs) after supernova explosions. Most of NSs are strongly magnetized including normal radio pulsars with B ∝ 1012 G and magnetars with B ∝ 1014 G. A fraction of 7–12 per cent of massive stars are also magnetized with B ∝ 103 G and some are weakly magnetized with B ∝ 1 G. It was suggested that m...

Stars of spectral types O and B produce neutron stars (NSs) after supernova explosions. Most of NSs are strongly magnetised including normal radio pulsars with $B \propto 10^{12}$ G and magnetars with $B\propto 10^{14}$ G. A fraction of 7-12 per cent of massive stars are also magnetised with $B\propto 10^3$ G and some are weakly magnetised with $B\...

Central compact objects (CCOs) are young neutron stars emitting thermal X-rays with bolometric luminosities L X in the range of 10 ³² –10 ³⁴ erg s ⁻¹ . Gourgouliatos, Hollerbach, and Igoshev recently suggested that peculiar emission properties of CCOs can be explained by tangled magnetic field configurations formed in a stochastic dynamo during the...

The role of magnetic field decay in normal radio pulsars is still debated. In this paper, we present results which demonstrate that an episode of magnetic field decay in hot young neutron stars can explain anomalous values of braking indices recently measured for more than a dozen of sources. It is enough to have few tens of per cent of such hot ne...

Central compact objects are young neutron stars emitting thermal X-rays with bolometric luminosities $L_X$ in the range $10^{32}$-$10^{34}$ erg/s. Gourgouliatos, Hollerbach and Igoshev recently suggested that peculiar emission properties of central compact objects can be explained by tangled magnetic field configurations formed in a stochastic dyna...

The role of magnetic field decay in normal radio pulsars is still debated. In this paper we present results which demonstrate that an episode of magnetic field decay in hot young neutron stars can explain anomalous values of braking indices recently measured for more than a dozen of sources. It is enough to have few tens of per cent of such hot NSs...

Recently, Parthsarathy et al. analysed long-term timing observations of 85 young radio pulsars. They found that 15 objects have absolute values of braking indices ranging ∼10–3000, far from the classical value n = 3. They also noted a mild correlation between measured value of n and characteristic age of a radio pulsar. In this article, we systemat...

Magnetars are neutron stars (NSs) with extreme magnetic fields of strength $5 \times 10^{13}$ - $10^{15}$ G. They exhibit transient, highly energetic events, such as short X-ray flashes, bursts and giant flares, all of which are powered by their enormous magnetic energy. Quiescent magnetars have X-ray luminosities between $10^{29}$ and $10^{35}$ er...

Recently, Parthsarathy et al. analysed long-term timing observations of 85 young radio pulsars. They found that 11 objects have braking indices ranging $\sim 10-100$, far from the classical value $n=3$. They also noted a mild correlation between measured value of $n$ and characteristic age of a radio pulsar. In this article we systematically analys...

The origin and evolution of magnetic fields (MFs) of young neutron stars (NSs) is an open question. MFs could be generated through a dynamo during the formation of NSs, or they could be a relic of a pre-supernova magnetic field. We want to test whether MFs of young NSs are the relics of their progenitors, massive OB stars. This could happen through...

Central Compact Objects (CCOs) are X-ray sources with luminosity ranging between 1032 and 1034 erg s−1, located at the centres of supernova remnants. Some of them have been confirmed to be neutron stars. Timing observations have allowed the estimation of their dipole magnetic field, placing them in the range ∼1010–1011 G. The decay of their weak di...

Understanding the natal kicks, or birth velocities, of neutron stars is essential for understanding the evolution of massive binaries and double neutron star formation. We use maximum likelihood methods as published in Verbunt et al. to analyse a new large data set of parallaxes and proper motions measured by Deller et al. This sample is roughly th...

Central Compact Objects (CCOs) are X-ray sources with luminosity ranging between $10^{32}$-$10^{34}$ erg~s$^{-1}$, located at the centres of supernova remnants. Some of them have been confirmed to be neutron stars. Timing observations have allowed the estimation of their dipole magnetic field, placing them in the range $\sim10^{10}$-$10^{11}$ G. Th...

Evolution of close binaries often proceeds through the common envelope stage. The physics of the envelope ejection (CEE) is not yet understood, and several mechanisms were suggested to be involved. These could give rise to different time-scales for the CEE mass-loss. In order to probe the CEE-time-scales we study wide companions to post-CE binaries...

We investigate the extent to which resonances between an oscillating background of ultra-light axion and a binary Keplerian system can affect the motion of the latter. These resonances lead to perturbations in the instantaneous time-of-arrivals, and to secular variations in the period of the binary. While the secular changes at exact resonance have...

We use maximum likelihood methods as published in Verbunt et al. to analyse a new large dataset of parallaxes and proper motions measured by Deller et al. This sample is roughly three times larger than number of measurements available before. For both the complete sample and its younger part ($\tau < 3$ Myr), we find that a velocity distribution co...

Evolution of close binaries often proceeds through the common envelope stage. The physics of the envelope ejection (CEE) is not yet understood, and several mechanisms were suggested to be involved. These could give rise to different timescales for the CEE mass-loss. Measuring the CEE timescales can, therefore, probe the physical processes involved...

The origin of ultrawide massive binaries (orbital separations 103-2 × 105 au) and their properties are neither well characterized nor understood. Here we use the second Gaia data release to search for wide astrometric companions to Galactic O-B5 stars which share similar parallax and proper motion with the primaries. Using the data we characterize...

We investigate the extent to which resonances between an oscillating background of ultra-light axion and a binary Keplerian system can affect the motion of the latter. These resonances lead to perturbations in the instantaneous time-of-arrivals, and to secular variations in the period of the binary. While the secular changes at exact resonance have...

The origin of ultra-wide massive binaries wider than >$10^3$ astronomical units (AUs) and their properties are not well characterized nor understood. Here we use the second Gaia data release to search for wide astrometric companions (orbital separations $10^3-$few$\times 10^5$ a.u.) to main-sequence Galactic O5-B5 stars which share similar parallax...

We use the Bayesian approach to write the posterior probability density for the three-dimensional velocity of a pulsar and for its kinematic age. As a prior, we use the bimodal velocity distribution found in a recent article by Verbunt, Igoshev & Cator (2017). When we compare the kinematic ages with spin-down ages, we find that in general, they agr...

We report on the first X-ray observation of the 0.28 s isolated radio pulsar PSR J1154-6250 obtained with the XMM-Newton observatory in 2018 February. A point-like source is firmly detected at a position consistent with that of PSR J1154-6250. The two closest stars are outside the 3σ confidence limits of the source position and thus unlikely to be...

In this note we propose that recently discovered radio pulsar J0250+5854 with 23.5 sec spin period is presently at the Hall attractor stage. This can explain low temperature and absence of magnetar-like activity of this source together with its spin period and period derivative. We present results of calculations of the evolution of this source in...

We report on the first X-ray observation of the 0.28 s isolated radio pulsar PSR J1154--6250 obtained with the XMM-Newton observatory in February 2018. A point-like source is firmly detected at a position consistent with that of PSR J1154--6250. The two closest stars are outside the 3$\sigma$ confidence limits of the source position and thus unlike...

Context. The mergers of neutron stars (NSs) and white dwarfs (WDs) could give rise to explosive transients, potentially observable with current and future transient surveys. However, the expected properties and distribution of such events is not well understood. Aims. Here we characterise the rates of such events, their delay-time distributions, th...

Recently, numerical calculations of the magnetic field evolution in neutron stars demonstrated the possible existence of a Hall attractor, a stage at which the evolution of the field driven by the Hall cascade ends. The existence of such a stage in neutron star magnetic evolution is very important, and can be potentially probed by observations. Her...

Several candidates for accreting magnetars have been proposed recently by different authors. Existence of such systems contradicts the standard magnetic field decay scenario where a large magnetic field of a neutron star reaches $\lesssim$ few$\times 10^{13}$G at ages $\gtrsim 1$ Myr. Among other sources, the high mass X-ray binary 4U0114+65 seems...

If the observed parallax ϖ′ has a gaussian measurement error σ, there is a 68% probability that the actual parallax ϖ is in the range ϖ′ − σ < ϖ < ϖ′ + σ (the frequentist approach). The probability distribution within this range is not known from ϖ′ and σ alone, and in particular, we cannot state that the most probable distance D is given by D = 1/...

We argue that comparison with observations of theoretical models for the velocity distribution of pulsars must be done directly with the observed quantities, i.e. parallax and the two components of proper motion. We develop a formalism to do so, and apply it to pulsars with accurate VLBI measurements. We find that a distribution with two maxwellian...

The aim of this work is to study the imprints that different models for black hole (BH) and neutron star (NS) formation have on the Galactic distribution of X-ray binaries (XRBs) which contain these objects. We find that the root mean square of the height above the Galactic plane of BH- and NS-XRBs is a powerful proxy to discriminate among differen...

It has long been unclear if the small-scale magnetic structures on the neutron star (NS) surface could survive the fall-back episode. The study of the Hall cascade (Cumming, Arras & Zweibel 2004; Wareing & Hollerbach 2009) hinted that energy in small scales structures should dissipate on short timescales. Our new 2D magneto-thermal simulations sugg...

We present a new method for probing the thermal electron content of the Galaxy by spectral analysis of background point sources in the absorption-only limit to the radiative transfer equation. In this limit, calculating the spectral index, $\alpha$, of these sources using a natural logarithm results in an additive factor, which we denote $\alpha_\m...

We use a Bayesian approach to derive the distance probability distribution for one object from its parallax with measurement uncertainty for two spatial distribution priors, a homogeneous spherical distribution and a galactocentric distribution-applicable for radio pulsars-observed from Earth. We investigate the dependence on measurement uncertaint...

We use a Bayesian approach to derive the distance probability distribution for one object from its parallax with measurement uncertainty for two spatial distribution priors, viz. a homogeneous spherical distribution and a galactocentric distribution - applicable for radio pulsars - observed from Earth. We investigate the dependence on measurement u...

We analyse the origin of the magnetic field decay in normal radio pulsars found by us in a recent study. This decay has a typical time scale $\sim 4 \times 10^5$~yrs, and operates in the range $\sim 10^5$~--~few$\times 10^5$~yrs. We demonstrate that this field evolution may be either due to the Ohmic decay related to the scattering from phonons, or...

We use a modified pulsar current analysis to study magnetic field decay in radio pulsars. In our approach, we analyse the flow not along the spin period axis as has been performed in previous studies, but study the flow along the direction of growing characteristic age, $\tau =P/(2\dot{P})$. We perform extensive tests of the method and find that in...

The variety of the observational appearance of young isolated neutron stars must find an explanation in the framework of some unifying approach. Nowadays it is believed that such scenario must include magnetic field decay, the possibility of magnetic field emergence on a time scale $\lesssim 10^4$--$10^5$ yrs, significant contribution of non-dipola...

Recently, Lee et al. used Gaussian mixture models (GMM) to study the radio pulsar population. P –Ṗ plane, they found four clusters. We develop this approach further and apply it to different synthetic pulsar populations in order to determine whether the method can effectively select groups of sources that are physically different. We check several...

Recently, Lee et al. used Gaussian mixture models (GMM) to study the radio pulsar population. In the distribution of normal pulsars in the P-dotP plane, they found four clusters. We develop this approach further and apply it to different synthetic pulsar populations in order to determine whether the method can effectively select groups of sources t...

We analyze different possibilities to explain the wide initial spin period distribution of radio pulsars presented by Noutsos et al. (2013). With a population synthesis modeling we demonstrate that magnetic field decay can be used to interpret the difference between the recent results by Noutsos et al. (2013) and those by Popov & Turolla (2012), wh...

We investigate the fortune of young neutron stars (NS) in the whole volume of the Milky Way with new code for population synthesis. We start our modeling from the birth of massive OB stars and follow their motion in the Galaxy up to the Supernova explosion. Next we integrate the equations of motion of NS in the averaged gravitational potential of t...

We consider the evolution of the very young neutron stars (NS) with moderate and low magnetic field values around 1E8 G to know how large is the share of the these objects among the those attributed as the millisecond pulsars (MSP). To exclude the contamination of accreted NS and young NS with moderate magnetic fields we study the observational evi...

We study the birth and evolution of isolated neutron stars in the Milky Way with new population synthesis code. We model the birth of massive OB stars and follow their motion within the spiral arms up to the supernova explosion. After that we consider the evolution of NS up to the death line with taking into account the magnetic field decay. We fin...

We investigate the properties of spin-down age curve in case of dipole electromagnetic radiation of neutron stars (NSs). It was found that that is independent from both initial period and magnetic field strength since 5·104 years age. Therefore, we restore the history of the magnetic field decay for the galactic NSs supposing that the laws of the f...

Using the data of the ATNF pulsar catalog we study the relation connected the real age t of young neutron stars (NS) and their spin-down age \tau. We suppose that this relation is independent from both initial period of the NS and its initial surface magnetic field, and that the laws of the surface magnetic field decay are similar for all NSs in th...

The properties of the spin-down age are investigated. Based on assumption about a uniform magnetic field decay law we suggest a new method which allows us to shed light on magnetic field decay. This method is applied for following selection: isolated non-millisecond pulsars from the ATNF catalog are chosen. Pulsars in the selection are with the spi...

Based on the newest measurements, statistical properties of rms mean magnetic fields of OB and neutron stars (NSs) were investigated. The magnetic field distribution function f(B) for OB stars was determined and a sharp decrease of f(B) for weak magnetic fields was found. The mean magnetic fluxes F for all massive stars and NSs with measured magnet...

The statistical properties of magnetic fields and magnetic fluxes of OB stars were investigated. The mean magnetic fluxes of massive OB stars appear to be 3 order larger than those for neutron stars.

Statistical properties of mean magnetic fields and magnetic fluxes of normal stars are investigated based on data from the catalogue of magnetic fields by Bychkov et al. (2009) and recent measurements from the literature. As a measure of the mean field, we use the rms longitudinal magnetic field B. We estimated the magnetic fluxes F of massive star...